Backing arrangement



tive bights extending oppositely to one another in directions from thecenter of the chair frame toward opposite sides of the latter and withsaid leg portions of each of said frame members diverging from oneanother foreand-aft of the chair frame; a resilient back and under-seatframe structure comprising a rear upstanding part and two laterallyspaced portions extending forwardly from the bottom of said rearupstanding part and each crossing the two side portions of respectiveones of said bights; and second means securing said laterally spacedportions to said bight side portions where said laterally spacedportions cross said bight side portions, the securing by said firstmeans at said single location and the securing by said second meansproviding the only securing of said resilient leg and under-seat framemembers and said resilient back and under-seat frame structure together,whereby said chair frame is resilient, enabling load thereon to bedistributed evenly through all four leg portions to a floor.

2. A chair frame construction according to claim 1 in which said secondsecuring means includes spacers interposed between and connecting eachof said laterally spaced portions and one of the side portions of therespective bights.

3. A chair frame construction according to claim 2 in which said spacersare respectively interposed between said laterally spaced portions ofsaid back and under-seat frame structure and the two foremost sideportions of said leg and under-seat frame member bights.

4. A chair frame construction according to claim 3 in which each of saidspacers comprises a U-shaped membed having two spacer legs and aconnecting part, said connecting part being dished to form a seat forthe associ-ated forwardly extending portion of said back and under-seatframe structure, and the spacer legs of each of said spacers beingdished transversely to the dishing of said connecting part to form seatsfor receiving the associated side portion of one of said leg andunder-seat frame members.

51 A chair frame construction according to claim 1 in which saidcombination leg and under-seat frame members and said back andunder-seat frame structure are metallic, and in which said securingmeans comprises welds.

6. A chair frame construction according to claim 1 in which said backand under-seat frame structure comprises a unitary elongated elementincluding an inverted V- shaped part constituting said upstanding part,said two laterally spaced portions respectively extending forwardly fromthe bottoms of opposite sides of said V-shaped part.

7. A chair frame construction according to claim 1 in which said bightsare inclined from the center of the chair frame towards the oppositesides thereof.

8. A chair frame construction according to claim 1 in which said bightsare inclined downwardly from the center of the chair frame towards theopposite sides thereof.

9. In a chair, a frame including two unitary combination leg andunder-seat frame members, each comprising an elongated resilient elementhaving intermediate its ends a bight including a central connectingportion and two side portions spaced from each other fore-and-aft of theframe and extending from opposite ends of said central connectingportion, said side portions terminating in continuing downwardlyextending mutually divergent leg portions; first means securing thecentral connecting portions of the bights of said two combination legand under-seat frame members together at a single location at the centerof said chair frame with the side portions of the respective bightsextending oppositely to one another in directions from the center of thechair frame toward opposite sides of the latter and with said legportions of each of said frame members diverging from one anotherfore-and-aft of the chair frame; a resilient back and underseat framestructure comprising a rear upstanding part and two laterally spacedportions extending forwardly from the bottom of said rear upstandingpart and each crossing above the two side portions of respective ones ofsaid bights; second means securing said laterally spaced portions tosaid bight side portions where said laterally spaced portions cross saidbight side portions, the securing by said first means at said singlelocation and the securing by said second means providing the onlysecuring of said resilient leg and under-seat frame members and saidresilient back and under-seat frame structure together, whereby saidchair frame is resilient, enabling load thereon to be distributed evenlythrough all four leg portions to a floor; :a back panel secured to saidrear upstanding part of said back and under-seat frame struc ture; and aseat p'anel secured on top of and to said forwardly extending portionsof said back and underseat frame structure.

10. A chair frame construction according to claim 9 in which said secondsecuring means comprises spacers respectively interposed between andconnecting each of said laterally spaced portions of said back andunder-seat frame structure and the foremost of the side portions of therespective bights, and in which said seat panel is downwardly dishedwith its central portion being disposed substantially directly above thesecured-together connecting portions of said bights, the side marginaledges of said seat panel being spaced above the junctures of said bightside portions and said downwardly extending mutually divergent legportions.

11. A chair frame construction according to claim 10 in which said seatpanel is yieldable.

12. A chair frame construction according to claim 10 in which said seatpanel has a down-turned marginal edge, the portion of said edgeextending across the back of the seat panel passing over said laterallyspaced forwardly extending portions of said back and under-seat framestructure and being supportable thereby.

13. A chair frame construction according to claim 10 in which said seatpanel is concave on its bottom adjacent its front and in which said backand under-seat frame structure is formed of a single piece of tubularmaterial, said two laterally spaced, forwardly extending portionsthereof terminating in front end parts which are closed and curvedconvexly on their upper surfaces to conform to the goncavity of the seatpanel bottom adjacent the seat panel 'ront.

References Cited by the Examiner UNITED STATES PATENTS D. 161,17712/1950 Harrison 297457 X 2,539,919 1/1951 Meek et a1 297451 2,815,80112/1957 Fingerhut et a1. 297 -451 2,961,037 11/ 1960 Keefer 29745 13,000,669 9/ 1961 Silverman 29745 1 3,201,172 8/ 1965 Bliss 297445 FRANKB. SHERRY, Primary Examiner.

CASMIR A. NUNBERG, Examiner.

O t 4 A. LUBBE ETAL ,27 19 BACKING ARRANGEMENT Filed Sept. 6, 1963INVENTORS ARM/IV 16535 W! HERBERT A'UTI'E/VB/MUCK United States PatentOifice 3,276,819 Patented Oct. 4, 1966 3,276,819 BACKING ARRANGEMENTArmin Liibbe, Oberaden Post Kamen, and Herbert Hiittenbrauck,Billmerich, Kreis Unna, Germany, assignors to Gewerkschaft EisenhuteWestfalia, Wethmar, near Lunen, Westphalia, Germany, a corporation ofGer- Filed Sept. 6, 1963, Ser. No. 307,244 Claims priority, applicationGermany, Sept. 7, 1962,

9 Claims. ((11. 299-32 The present invention relates to a backingarrangement for lateral urging abutment against a mining conveyoradapted to extend longitudinally along a mine face to urge such conveyortoward the mine face, especially wherein such conveyor is provided withtrack means thereon upon which a planer is slidably mounted for back andforth movement of such planer while in extractive engagement with themine face. More particularly, the present invention relates to such abacking arrangement, preferably hydraulically operated, in which asecondary or auxiliary urging means is provided linkably interconnectedwith the main urging means through an abutment bar, whereby such bar maybe angularly displaced in a vertical plane for changing the resultantdirection of force of the backing arrangement when placed against amining conveyor with the abutment bar in urging contact with the side ofthe conveyor remote from the mine face.

Where minerals, such as coal, are mined or extracted by scrapingmethods, as for example using a planer guided on a conveyor for back andiorth movement along the mine face, the harder the mineral, for examplecoal, becomes the more diflicult it is to guide the planer consistentlyso that it cuts the coal or other mineral loose from the mine faceprecisely at the floor level of the mine. Of course, for the desiredresults to be achieved, the planer must not penetrate, or at least mustnot penetrate too deeply, into the mine floor, but neither should theplaner be permitted to turn out of the coal face, ie be transverselydisplaced from the coal face, for instance, where the coal beingextracted is so hard that the planer backs off.

It is an object of the present invention to overcome the foregoingdrawbacks and to provide a backing arrangement for conveyors, especiallywhere the conveyor is equipped with a planer guided for back and forthmovement thereon, whereby the conveyor may be satisfactorily urgedtoward the mine face, with the conveyor and in turn the planer beingmaintained precisely at the desired level with respect to the minefloor.

Other and further objects of the invention will become apparent from astudy of the within specification and accompanying drawing in which:

FIG. 1 is a schematic elevational view of a backing arrangement inaccordance with one embodiment of the invention showing the backingarrangement in position against a longitudinally extending miningconveyor, and

FIG. 2 is a schematic elevational view, partially in section, of anotherembodiment of the backing arrangement in accordance with the presentinvention, also :shown adjacent a longitudinally extending miningconvey-or.

It has been tound in accordance with the present invention that abacking arrangement of versatility and effectiveness may now be providedfor lateral urging abutment against a mining conveyor adapted to extendlongitudinally along a mine face to urge such conveyor toward the mineface, especially where the mining conveyor is equipped with track meansfor slidably mounting a planer thereon for back and forth movement ofthe planer while in extractive engagement with the mine face. Thebacking arrangement of the invention generally comprises base means forengaging the mine floor and mine ceiling, first urging means and secondurging means operatively connected to the base means, each said urgingmeans including a linearly displaceable urging member having a free endremote from said base means, the linear displaceable member of one ofsaid urging means being operatively situated above the displaceablemember of the other urging means, and an abutment bar disposed in asubstantially vertical plane and pivotally connected by a separate pivotto each of said free ends to linkablywinterconnect said members at theirfree ends and to permit angular displacement of said bar in saidvertical plane in response to linear displacement of at least one ofsaid displaceable members. In this way, during abutment of the baragainst the side of the conveyor remote from the mine face, the firstand second urging means will urge the conveyor toward the mine face witha resultant direction of force which varies in dependence upon theangular disposition of the abutment .bar with respect to the mine floor.

Conveniently, the urging means in each instance may comprise apiston-cylinder arrangement including a piston part and a cylinder part,one of said parts being the corresponding linearly displaceable urgingmember and the other of said parts being operatively connected to thebase means. The base means more specifically may include a supportingleg for engaging the mine floor 'and prop means mounted on said leg forengaging the "more effectively. Also, one of the piston-cylinderarrangements in this instance is pivotally connected by one of its partsto the supporting leg and by the other of its parts to the abutment bar.,Resilient means are provided on the supporting leg in this connectiontor normally downwardly urging such one piston-cylinderarrangementintermediate the pivotal connections thereof. Moreover, theother of the piston-cylinder arrange ments may be operatively connectedto the base means via said other of the parts of said onepiston-cylinder arrangement with one of the corresponding parts of saidother piston-cylinder arrangement being fixed to said other of the partsof said one piston-cylinder arrangement and with the other of thecorresponding parts of said other piston-cylinder arrangement beingpivotally connected to the abutment bar.

In accordance with an alternate feature of the present invention, theprop means may take the form of a vertical prop mounted on thesupporting leg for engaging the mine ceiling, with a carriagehorizontally displaceably mounted on the supporting leg. In thisinstance, one of the piston cylinder arrangements may be pivotallyconnected by one of its parts to the supporting leg and by the other ofits parts to the abutment bar, said other of its parts being alsoconnected at least along a portion thereof to said carriage.Additionally, the other of said piston-cylinder arrangements may beoperatively connected to the base means via said carriage with one ofthe corresponding parts of said other piston-cylinder arrangements beingoperatively connected to the carriage and with the other of thecorresponding parts of said other piston-cylinder arrangements beingpivotally connected to the abutment 3 1 bar.- More specifically, thesupporting leg in this regard may be provided with an upper retainingmeans and a lower retaining means, said retaining means being verticallyspaced apart, and the carriage may be provided in turn with an upperslide surface and a lower slide surface, such that a portion of thecarriage is displaceably received within the supporting leg with avertical clearance between the upper slide surface and the upperretaining means and with the lower slide surface in sliding engagementwith the lower retaining means. Adjustable shim. means also may beprovided effectively in the vertical clearance in question to limitadjustably the upward displacement of the carriage with respect to thesupporting leg.

Advantageously, the other piston-cylinder arrangement may be furtherprovided with a damping means operatively connected between said one ofthe corresponding parts of said other piston-cylinder arrangement andsaid carriage for absorbing excessive forces exerted on said otherpiston-cylinder arrangement during abutment of the bar against theconveyor.,

In accordance with one particular embodiment of the invention,hydraulically operated piston-cylinder means are provided in addition tothe usual bracing pistoncylinder means, such that pressure components ofvarious magnitude may be exerted on the mining conveyor and/ or planerguide means depending upon the extent to which the adjustingpiston-cylinder arrangements are stressed to change the angle of theabutment bar with respect to its normal ,verticalposition. Thus, theresultant components of force may be exerted such that the over-allforce is directed diagonally downwardly toward the mine floor ordiagonally upward toward the mine ceiling, in addition to the normalhorizontal direction toward the mine face, for overcoming an adverseposition of the conveyor on the mine floor, so as to preventthe-conveyor from lift ing from its normal position or from diggingundersirably downwardly into a soft area in the mine floor. By avoidingsuch possibilities, through suitable adjustment of the backingarrangement and in turn the planer guide and/ or conveyor, the planerwill always be guided along its true longitudinal course, preciselyalong the horizontal level of the mine floor desired.

Referring to the drawing, in FIG. 1, a backing arrangement is shown inaccordance with one embodiment of the invention, including a base meansof U-shaped construction, with the free ends of the U downwardly facing,

a pit prop 11 being pivotally mounted by pivot 12 onto the supportingleg 10 at an angle with the mine floor sufficient to brace the basemeans against any displacement thereof in the direction toward the leftas viewed in FIG. 1. A main piston-cylinder arrangement 13 including apiston 14 and a cylinder 15 is provided as well as a secondarypiston-cylinder arrangement 16 including the secondary cylinder 17 andthe secondary piston 18. The piston-cylinder arrangements 13 and 16 areconnected linkably via the normally vertical abutment bar 19. Morespecifically, main piston 14 is pivotally connected by pivot 20 tosupporting leg 10 and main cylinder 15 is pivotally connected toabutment bar 19-=by pivot 21, whereas secondary cylinder 17 is fixedlyconnected to the upper side 22 of main cylinder 15 while secondarypiston 18 is pivotally connected by pivot 23 to abutment bar 19.

A longitudinally extending mining conveyor 27 of con ventionalconstruction is shown having the side members 28 and 29 which areinterconnected intermediate their height by trough plate 30. On sidemember 29 a suitable guiding track 31' in the form of a guiding tube isprovided such that a planer of the usual type may be mounted thereon formovement back and forth along the mine face adjacent that side of theconveyor. In this connection, the conveyor in question may be of theusual double chain scraper conveyor type such as that shown in US.Patent 2,810,565, issued October .22, 1957, and US. Patent 2,990,168,issued June 27, 1961. Usually the coal or other mineral, extracted bythe planer from the mine face is loaded onto the conveyor and hauledtherealong by a scraper .bar mechanism comprising parallel chainsinterconnected along their common length by scraper bars for conveyingthe coal from the site of extraction.

In order to ensure a firm grip with the mine floor, the under side ofthe supporting leg 10, i.e. for example, along the free ends of theU-shaped portion may be provided with downwardly extending projections24 which sink into the mine floor. Inasmuch as there may be a tendencyfor the main piston-cylinder arrangement 13 to rotate upwardly about theaxis of pivot 20; a loaded spring 25 within a casing 26 is downwardlyurged against the upper portionof main cylinder 15 to. oflset any suchupward pivotal displacement of the piston-cylinder arrangement As willbe appreciated, the secondary or auxiliary piston-cylinder arrangement16 may be utilized to move the upper pivot 23 farther toward the mineface than the pivot 21 so as to counteract any upward .dsiplacement ofthe side member'28 of the conveyor 27 which might result in buckling ofthe arrangement or :the causing of the fcylinder 15 is connected to' thebar .19 such that main cylinder 15 abuts the side member 28 of theconveyor 27 approximately at the height of the trough plate 30. In

this way, main piston-cylinder arrangement 13 .will normally urge theconveyor 27 in the horizontal direction, i.e. at the height of thetrough plate 30. By the presence of the secondary piston-cylinderarrangement 16, a higher point of engagement at pivot 23 is provided,such that if secondary piston 18 is urged toward the conveyor 27, -aresultant force is produced via the abutment bar 19 which is directedslantingly downwardly toward the. coal face, such as in the direction ofthe arrow-32.

While the presence of the secondary piston-cylinder arrangement 16connected to the main cylinder 15 might otherwise cause a rotation ofthe arrangement about the pivot 20 on the supporting leg 10, due to thepresence of the downwardly urging spring 25, any such tendency issuitably offset. At least, any unilateral lifting of the conveyor in themanner shown in FIG. 1 is minimized by the presence of the spring 25 onthe base means.

Where the secondary piston-cylinder arrangement 16 is operated, suchthat the piston 18 moves away from the conveyor 27, the guiding track 31might be caused to press against the coal face with a component of forcedirected slantingly upwardly rather .thanas shown by arrow 32. In suchcase, the digging 'of the planer. into the mine floor would beprevented, even if the mine floor were soft and friable.

Naturally, the positioning of the main piston-cylinder arrangement andthe secondary piston-cylinder arrangement may be reversed, such that themain piston-cylinder arrangement is situated above the secondarypiston-cylinder arrangement, yet with the construction permitting thedesired angular displacement of the abutment bar 19.. Moreover, it willbe appreciated thatthe secondary pis- -ton-cylinder arrangement maybeconnected directly or indirectly, and fixedly or pivotally onto the mainpistoncylinder arrangement. Furthermore, the angle of pivot of the mainpiston-cylinder arrangement 13 about the pivot 20 maybe suitably limitedby the provision for ad- 'justable stop means on the supporting leg 10,i.e.. above and below the normal horizontal position of the main piston14 to prevent toohigh or too low a movement of piston 14 w-ithrespect tothe normal horizontal disposition thereof. It will be appreciated, fromFIG. 1, that by providing the supporting leg 10 as a U-shaped memberwith the free ends of the U directed downwardly, the mainpiston-cylinder arrangement 13 will be suitably protected from coal,dirt, dust, etc. which might otherwise clog and damage the operatingparts.

As will be appreciated by the artisan, any conventional means may beemployed for actuating the piston-cylinder arrangements 13 and 16, aswell as the pit prop 11 which may be extended or retracted. Usually, thepit prop takes the form of a hydraulic jack and the piston-cylinderarrangements take the form of hydraulically operated pistons of thedouble-acting type. More specifically, a reservoir for hydraulic fluidmay be connected via separate lines to each end of the particularcylinder in question so that hydraulic fluid may be injected or removedfrom that portion of the cylinder on the appropriate side of the piston.Such arrangements are Well known and need not be exemplified furtherherein. The operation to be achieved in any case, of course, is that thepiston and cylinder may be actuated to urge the same further into andfurther out of telescopic engagement with one another, depending onwhether the linear displacement desired is to increase the distancebetween the free end of the piston and the free end of the cylinder orto decrease such distance. This will immediately affect the angulardisposition of the abutment bar 19 with respect to the mine floor.

With respect to FIG. 2, an alternate embodiment of the invention isshown including a base means having a supporting leg 33 situated on themine floor and a vertical prop 34 for engaging the mine ceiling, wherebythe base means will be fixed against undesired horizontal displacementthereof. The supporting leg 33 is provided with an upper retaining means35 and a lower retaining means 36 which are vertically spaced apart fromone another such that the carriage 37 which is provided with an upperslide surface 38 and a lower slide surface 39, may be horizontallydisplaceably received at least along one end portion thereof within thespace between the retaining means 35 and 36. In order to prevent undueupward displacement of carriage 37 within the space between theretaining means 35 and 36, adjustable shims are provided in stackedrelation between the upper slide surface 38 and the retaining means 35.While the carriage 37 may be displaced in horizontal direction in anundisturbed manner, even though shims 40 are present, this is becausethe shims are suitably retained against horizontal displacement. Ifdesired, other stop means may be used in place of the shims 40 to limitthe upward displacement of the carriage 37.

In the embodiment of FIG. 2, the main piston-cylinder arrangement isdisposed above the secondary piston-cylinder arrangement. Thus, mainpiston 41 slidably received within main cylinder 42 is pivotallyconnected at its free end to supporting leg 33 by pivot 43, maincylinder 42 being pivotally connected to the abutment bar 45 by thepivot 44. On the other hand, the secondary cylinder 46 is provided witha partition 47 so as to form a separate damping cylinder compartment 48in which the damping piston 49 is slidably received, the free end ofdamping piston 49 being pivotally connected to the car-riage 37 at pivot50. At this point, it should be noted that while damping piston 49 ispivotally connected to the carriage 37, the main cylinder 42 is fixedlyconnected along at least a portion of its length to the carriage 37whereby a change in the disposition of main piston 41 within maincylinder 42 will cause the horizontal displacement of carriage 37 withrespect to supporting leg 33, while this will not be always true in thecase of damping piston 49 and damping cylinder compartment 48.Specifically, secondary piston 51 attached at its free end by pivot 52to the abutment bar 45 is received within secondary cylinder 46 so as tourge abutment bar 45 against the side member 28 of the conveyor 27.Nevertheless, since cylinder 46 is in fact connected with the dampingcylinder compartment 48 due to the presence of the partition Wall 47,and since the damping cylinder compartment 48 is operatively connectedwith the damping piston 49, undue stresses met by the conveyor uponpassage of the planer therealong in engagement with the mine face, willbe absorbed by the damping action of piston 49 within chamber 48. Thisis true since chamber 48 is connected with the reservoir for thehydraulic fluid used for operating the arrangement as noted above inconnection with the oper-ation of the pistons and cylinders in FIG. 1.The reservoir pressure will return the damping piston 49 to its normaldisposition 49 within the cylinder chamber 48 once the excessive forcehas been relieved, due to the maintainen-ce of a reference pressurewithin the reservoir for the hydraulic fluid. However, in the case ofcylinders 42 and 46, these cylinders are provided preferably at the endsof the cylinder chambers with hydraulic fluid connections for injectingor withdrawing hydraulic fluid from the .approprate sides of the pistonin question. Therefore, the piston-cylinder arrangements may be operatedto increase or decrease their length in the usual manner. The same istrue with respect to the vertical prop 34 which may take the form of ahydraulic jack similar to the slanting jack 11 of FIG. 1, both suchjacks being extensible or retractable as desired.

It will be appreciated that while FIG. 1 is directed to an embodiment inwhich the main piston-cylinder arrangement is situated below thesecondary piston-cylinder arrangement, in FIG. 2 just the oppositeconstruction is achieved. Naturally, the shock absorbing or yieldingaction provided by the damping piston 49 within the damping cylindercompartment 48 may be utilized in accordance with the embodiment of FIG.1 as well by merely connecting the piston-cylinder arrangement 16 ofFIG. 1 with the piston-cylinder arrangement 13 by a dampingpiston-cylinder arrangement, etc.

In the case of FIG. 2, the planer guiding track or tube 31 may bepressed against the mine face by the urgence of cylinder 42 under theaction of hydraulic pressure against piston 41, such that the point ofexertion of the hydraulic force against the side member 28 will beadjacent the pivot 44 of the abutment bar 45. This point issubstantially above the intermediately positioned trough plate 30 of theconveyor 27. Thus, if only the main piston-cylinder arrangement isactuated, the track 31 will be urged against the coal face with adownwardly slanting direction of force. In order to prevent the conveyor27 from lifting from the mine floor at its rear side and in turn thelifting of the main piston-cylinder arrangement about the pivot point43, the supporting leg 33 is supplied with appropriate stop means, inthe embodiment shown such stop means taking the form of adjustable shims40. Of course, the number of stacked shims 40 and hence the stoppingpoint in upward direction of the carriage 37 and in turn the cylinder 42can be adapted to the prevailing conditions in each case by adding orsubtracting one or more shims from the number then being used.

'Iihe construction of the present invention advantageously permits anaccurate and precise urgence of the force of the backing arrange-ment ina particular direction. Thus, in the embodiment of FIG. 2, for instance,if it is desired to urge the conveyor 27 at the side member 28 with afonce directed approximately parallel to the mine floor, the secondarycylinder 46 may be appropriately actuated to cause the correspondingmovement of the secondary piston 51 and in turn the varying of theangular disposition of the abutment bar 45. The presence of the dampingpiston-cylinder arrangement connected to the hydraulic fluid reservoiror pressure line permits a desired urging pressure to be exerted againstthe conveyor, not only with the normal force of the cylinder 42 but alsowith the yieldable force of the cylinder 46, coupled with the dampingcylinder compartment 48. By suitable adjustments of the length ofextension of piston 51 and cylinder 42, the desired pressure component

1. BACKING ARRANGEMENT FOR LATERAL URGING ABUTMENT AGAINST A MININGCONVEYOR ADAPTED TO EXTEND LONGITUDINALLY ALONG A MINE FACE TO URGE SUCHCONVEYOR TOWARD THE MINE FACE, WHICH COMPRISES UNITARY BASE MEANS FORENGAGING THE MINE FLOOR AND MINE CEILING, FIRST URGING MEANS AND SECONDURGING MEANS, EACH SAID URGING MEANS BEING OPERATIVELY CONNECTED TO SAIDBASE MEANS, EACH SAID URGING MEANS INCLUDING A LINEARLY DISPLACEABLEURGING MEMBER HAVING A FREE END REMOTE FROM SAID BASE MEANS, THE LINEARDISPLACEABLE MEMBER OF ONE OF SAID URGING MEANS BEING OPERATIVELYSITUATED ABOVE THE DISPLACEABLE MEMBER OF THE OTHER URGING MEANS, ANABUTMENT BAR DISPOSED IN A SUBSTANTIALLY VERTICAL PLANE AND PIVOTALLYCONNECTED BY A SEPARATE RESPECTIVE PIVOT TO EACH OF SAID FREE ENDS TOLINKABLY INTERCONNECT SAID MEMBERS AT THEIR FREE ENDS AND TO PERMITANGULAR DISPLACEMENT OF SAID BAR IN SAID VERTICAL PLANE IN RESPONSE TOLINEAR DISPLACEMENT OF AT LEAST ONE OF SAID DISPLACEABLE MEMBERS,WHEREBY DURING ABUTMENT OF SAID BAR AGAINST THE SIDE OF SUCH CONVEYORREMOTE FROM THE MINE FACE SAID FIRST AND SECOND URGING MEANS WILL URGESAID CONVEYOR TOWARD THE MINE FACE WITH A RESULTANT DIRECTION OF FORCEWHICH VARIES IN DEPENDENCE UPON THE ANGULAR DISPOSITION OF SAID BAR WITHRESPECT TO THE MINE FLOOR.